It is known that new recording apparatus, called "cassette" recorders, having low cost, and limited performance and storage capacity, recently have been introduced into electronic data handling systems.
These cassette recorders are used, for example, as low-capacity storage means in computer terminals, or in small data handling systems, and as input means for loading programs and sets of data, in place of other more complex, bulky and expensive input-output apparatus such as card punchers and readers.
In the cassette recorders used in data handling devices, the information is recorded in digital form, according to methods such as the "Non Return to Zero" method, or preferably, the "Phase Modulation" method, which allows a higher recording density. The data is usually recorded on two parallel tracks, extending along the whole length of the tape, and a single-track magnetic head may be employed, which operates on one track at a time. It is usually required that the written information is capable of being immediately read out, for checking purposes: therefore the magnetic head usually comprises a writing and erasing transducer, and a reading transducer, arranged in succession at a small distance, and in this order with respect to the direction of the tape.
According to known arrangements, as soon as the recording and/or reading of a track has been accomplished, the cassette containing the tape is removed from the recorder and re-introduced therein after having been rotated 180.degree., so that the same head is used for recording or reading on the second track. This arrangement has several inadequacies.
In the first place, it must be kept in mind that data handling devices using tape cassettes drive the tape at higher speed than commercial and entertainment recording and playback devices. The speed of operation may be, for instance, 7 or 14 inches per second, corresponding to 19.5 or 39 cm per second respectively: therefore the time for recording or reading a whole track does not exceed respectively 8' or 4'.
The task of stopping the recorder, removing the cassette, rotating it by 180.degree., replacing the same into the recorder and restarting the operation on the other track involves a dead time, during which the apparatus is inactive. Such dead time, even if it may account only for a small percentage of the recording-reading time of a track, noticeably affects the overall performance.
Secondly, the manual inversion of the cassette, which usually is placed in a closed and dust-proof compartment, exposes the same to atmospheric agents and allows dust and other noxious external materials to enter and accumulate in the compartment, thus causing abrasion and damages to the tape, to the driving mechanism and to the magnetic head.
To remove such drawbacks it has been proposed recently, for instance, to equip the data handling cassette recorder with a magnetic head mounted on a rotatable support, capable of a rotation of 180.degree., by means of an electromagnetic control device for bringing the head in registration with the second track, thus avoiding the need for removing and replacing the cassette.
This arrangement involves contrivances, complex in design, and may impair the precision of the relative positioning of the head and the tape, mainly with respect to the orthogonality of the head gap to the direction of the tape.